This invention relates to an infrared and ultraviolet radiation absorbing glass and a method of producing the glass. The glass has a bluish color and sufficiently high transmittance for visible light and is particularly suitable for use in building and vehicle windows.
For windows of buildings, automobiles and other vehicles there is an increasing demand for sheet glass that is sufficiently transparent to visible light and absorptive of not only infrared rays but also ultraviolet rays.
It is known to render a soda-lime silica glass absorptive of infrared and ultraviolet rays by incorporating iron in the glass. Ferrous iron expressed as FeO provides for the absorption of infrared radiation, whereas ferric iron expressed as Fe.sub.2 O.sub.3 provides for the absorption of ultraviolet radiation. In practice Fe.sub.2 O.sub.3 is used as the source of the entire iron, and an adequate portion of Fe.sub.2 O.sub.3 is reduced to FeO during the glassmaking process.
Also it is known to incorporate CeO.sub.2 and/or TiO.sub.2 in a soda-lime silica glass for the absorption of ultraviolet radiation.
From an industrial point of view it is desired that an infrared and ultraviolet absorbing glass in the form of sheet glass can be produced without significantly changing the conditions of conventional glass melting and refining operations. Also it is desired that an infrared and ultraviolet absorbing glass sheet can easily be toughened by a conventional tempering method. Besides, an infrared and ultraviolet absorbing glass sheet is desired to have a pleasing tint such as a greenish tint or a bluish tint.
U.S. Pat. No. 4,792,536 shows an infrared and ultraviolet absorbing glass and a method of producing same. Basically the glass is a soda-lime silica glass. In the glass the content of total iron expressed as Fe.sub.2 O.sub.3 is up to 1 wt %, and preferably 0.45-0.65 wt %, and at least 35% of the total iron is in the ferrous state as FeO. Besides, the glass contains up to 1.5 wt % of CeO.sub.2 and/or TiO.sub.2. An important feature of the glass of this patent is that the content of SO.sub.3 is less than 0.02 wt %.
From an industrial point of view the proposal of U.S. Pat. No. 4,792,536 is not favorable because the proposed glass cannot be produced by the conventional glass-melting operations. As is disclosed in the patent specification, due to the very low content of sulfur it is necessary to employ a complicated two-stake melting and refining operations by using a special stirring means.
U.S. Pat. No. 4,701,425 shows an infrared and ultraviolet absorbing glass which is basically a soda-lime silica glass and contains 0.29-0.6 wt % of iron expressed as Fe.sub.2 O.sub.3, 0.1-1.5 wt % of SnO.sub.2 and 0.1-1.6 wt % of TiO.sub.2. It is permitted that the glass contains up to 0.5 wt % of SO.sub.3. However, this glass is insufficient in the capability of absorbing both infrared rays and ultraviolet rays, and it is not easy to desirably toughen this glass by a conventional tempering method.
U.S. Pat. No. 5,013,487 shows an infrared absorbing blue-colored glass containing 0.3-0.7 wt % of iron expressed as Fe.sub.2 O.sub.3, up to 0.5 wt % of TiO.sub.2, up to 0.6 wt % of SnO.sub.2 and 0.5-1.2 wt % of ZnO. This glass is low in the absorption of ultraviolet rays.